Add job action button to PMG

What does this MR do and why?

Part 1 of 3 for #467279 (closed)

• Part 1 - Render job action buttons < you are here
• Part 2 - Job action mutations
• Part 3 - Confirmation modal

This MR renders the job action buttons. For now, we are just showing the buttons in the dropdown. Clicking on them currently is not wired in and will simply navigate to the job.

Screenshots or screen recordings

How to set up and validate locally

Prerequisites

• An enabled feature flag: Feature.enable(:ci_graphql_pipeline_mini_graph)
• A working runner

Steps

1. Navigate to a project (this example uses the flightjs group)
2. Navigate to the Pipeline Editor (Build > Pipeline editor)
3. Trigger a pipeline
4. Once the pipeline appears in the pipeline editor widget, click on a stage
5. You should see the dropdown with a list of jobs and action buttons

Example gitlab-ci.yml if you'd like to see different job types

job: 
  script:
    - sleep 5
  when: delayed
  start_in: 2 minutes

another_job:
  script:
    - sleep 5
  when: manual

another_job_2:
  script:
    - sleep 15
  when: on_failure